Fluid servomotor actuated tool



May 1, 1956 Filed Jan. 27, 1955 R. KELLERSMAN 2,743,707

FLUID SERVOMOTOR ACTUATED TOOL.

2 Sheets-Sheet 1 INVEN'I'OR. E0551? 717654 A ERSM/IN ATTORNEYS y 1956 R. KELLERSMAN 2,743,707

FLUID SERVOMOTOR ACTUATED TOOL.

Filed Jan. 2'7, 1953 2 Sheets-Sheet 2 INVENTOR. ROBE/e 7 KELLEESMAN BY 'QTTORNEYS United States Patent FLUID SE VQMOTQR AG U TE T Robert Kellersman, Salem, Greg. Application January 27, 1953, semi No. 333,464 4 Claims. (Cl, 1Z14 1) This invention relates generally to an air servomotor actuated tool.

The particular embodiment of the inventionwhich is illustrated in the drawings comprises pneumaticallyoperated cutting shears. Such shears have been found to have particular utility in cutting off chicken legs adjacent the hock joints thereof inwaccordance with. customary practice in commercial chickeneviscerating plants. Although the more detaileddiscussion of the invention which hereinafter follows will be with particular reference to cutting shears, it is understood that the principles of construction and operation of the invention will have applicability to other types of tools having atworking part (such as a cutting blade) which is adapted to be forcefully moved through a working strokefrom a rest position to a working position under influence of pneumatic pressure.

A principal object of the invention is to provide a pneumatic piston operated tool of the character above mentioned, and which is constructed in such manner as to permit an operator to substantially instantaneously stop movement of the working part of the instrument at any time during a working stroke. Many conventional and commercially available pneumatic tools of which I have knowledge, and which have working parts adapted to operate, through connection to an air piston and cylinder unit, do not provide any means for instantly stopping movement of the working part during a working stroke until the piston has moved to a predetermined position with the cylinder whereat air is automatically exhausted. In such tools, even if the air supply to the cylinder is shut off prior to completion of a given work stroke, the air pressure contained within the cylinder will continue to exert pressure against the piston and cause it to move toward its predetermined exhaust position. As above noted, a device embodying the present invention is so constructed as to operate automatically andsubstantially instantaneously to stop movementof the driving piston and its associated working part of the tool uponshutting off of fluid pressure to the cylinder at any time after commencement and before completion ofa working stroke of the piston within its cylinder.

One principal purpose and advantageof such arrangement is to insure maximum safety in operation. Thus, for example, if at any time during operation of the device an unsafe condition should suddenly arise, such as, for instance, should an operators clothing or part of his person get in the way of or become entangled with the moving working part of the tool, the, device maybe substantially instantaneously stopped and maintained inoperative until such time as the dangerou's condition is remedied.

Another principal reason for constructing a device is so that control over its operation is maintained at all times.

In certain typesofwork it is frequently desirable to an operator commences the cut in the wrong place and which, if completed, might render the bird unsuitable for packaging and sale. In using shears of the present type, should an operator determine at the commencement of the cutting stroke that the blades are improperly positioned, he may substantially instantly stop further operation of the device and commence cutting operations anew.

Other objects of the invention are toprovide a pneu matic tool of the character briefly mentioned abovewhich does not require any special skill to operate and which may be relatively economically manufactured,- operated, and maintained.

Other objects and advantages of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

Fig. l is a side elevational view of pneumatic cutting shears embodying the invention showing certain portions thereof in section.

Fig. 2 is a top plan view of the tool partially in section.

Fig. 3 is a sectional view taken on line 33 of Fig. 2.

Fig. 4 is an enlarged longitudinal sectional view of the piston cylinder assembly showing the parts in rest position.

Fig. 5 is an enlarged longitudinal sectional view of the piston cylinder assembly showing the relative position of the parts during a working stroke.

Referring now more specifically to the drawings, the pneumatic shears embodying the invention are shown as comprising, generally, a frame and grip assembly A, cutting blade assembly B, trigger assembly C,. a cylinder assembly D, and a piston assembly E.

The frame and grip assembly, heretofore designated generally at A, is shown as comprising a frame plate 11 to which is rigidly secured a depending hollow handle grip 12. Said plate also operatesto rigidly support the cylinder and piston assemblies D and E as well as the blade and trigger assemblies B and C. i

The blade assembly B comprises, more specifically, a stationary lower blade 13 and a moving blade 14 pivotally connected to said stationary blade 13 and to frame plate 11 by pivot pin 15. Said blades are normally main; tained in open position by force of conventional clock spring 16, and which saidspring also acts to retract piston unit A to its rest position upon exhaust of air from which cylinder D, as will more fully appear hereinafter. In this regard it is noted that blade 14 is operatively connected to piston unit E by means to be hereinafter described.

Trigger assembly C comprises, more specifically, a depending trigger 17 pivoted to frame 11, as at 18, u and provided with an upwardly projecting integral extension piece 19, which latter element is operatively connected to the air inlet valve means, as will more fully appear hereinafter. Flat spring 20 is adapted to normally maintain trigger 17 urged away from handle grip 12.

Cylinder assembly D is of generally conventional construction comprising a cylinder head plate 21 and side walls 22. The end of the cylinder opposite head 21 is open to accommodate the various connecting parts to be described hereinafter which extend from the piston unit outwardly of the cylinder. The head end of the cylinder may also be provided with adjustable stop or abutment means, such as threaded bolt 23, which extends interiorly of the cylinder and is adapted to maintain the piston unit in spaced position away from said head when the piston is at rest.

The piston unit, heretofore designated generally at E, is mounted within the cylinder for slidable reciprocal movement therein through a working stroke from an inoperative or rest position adjacent cylinder head 21 toward the open end of the cylinder. More specifically, the piston unit may comprise upper and lower body portions 26 and 27, respectively, rigidly clamped and joined to one another as by conventional bolts 28. Adjoining ends of the upper and lower body portions are recessed defining an enlarged interior cavity, indicated at 29. Extending transversely of cavity 29 is a resilient diaphragm 31 clamped around its periphery between the upper and lower body portions of the piston unit. Diaphragm 31 functions to partition enlarged cavity 29 into separate upper and lower chambers, indicated at 32 and 33, respectively.

Upper chamber 32 is vented to atmosphere via port 34 formed through lower body portion 27. Preferably an expansion spring 36 is also provided in said upper chamber 32 to maintain diaphragm 31 normally spring biased toward lower body portion 27, and for reasons which will more fully appear hereinafter.

A centrally located circular inlet tube 37 is projected slidably through the lower body portion 27 of the piston unit and is threadedly secured, as at 38, at its inwardly projecting end to valve member 39 disposed Within lower chamber 33. Valve member 39 is mounted on resilient diaphragm 31 and comprises, more specifically, a disklike body portion, provided with an annular gasket seat 42 and formed with a centrally disposed air passage 43 defining a valve seat 44 telescoped within the upper end extremities of inlet tube 37. Said valve member 39 is also formed with a transverse passage 45 connecting lower chamber 33 with passage 43.

As will more fully appear hereinafter, compressed air from a suitable compressory source (not shown) located exteriorly of the cylinder may be supplied to the tool via flexible hose 46, which extends through hollow handle grip 12 and is connected as at 47 to inlet tube 37.

Transverse passages 48, formed through the side Walls of the piston unit, connect with longitudinal grooves 49, formed about the periphery of upper body portion 26, and thereby establish communication between chamber 33 and the head side of cylinder D.

A plurality of exhaust ports 41, formed longitudinally through lower body portion 27 of the piston unit, function to connect lower chamber 33 with atmosphere upon opening of valve member 39. Valve member 39 is normally maintained resiliently seated against said exhaust ports by resilient diaphragm 31, carrying said valve member, and its associated spring 36.

Control of air supply to the cylinder is effected through operation of valve stem 52 mounted slidably within inlet tube 37, which said stem carries valve head 53 engageable against valve seat 44 defined by air passage 43. Valve stem 52 is substantially smaller in diameter than the inner diameter of inlet tube 37 so as to establish an annular air passage between said stem and the exterior walls of the inlet tube. A suitable bushing or stufiing box 54 is provided to prevent escape of air through the lower end of inlet tube 37 and yet permit the stem to be slidably reciprocated within said inlet tube into and out of seating engagement with valve seat 44.

The outer projecting end of stem 52 is connected pivotally to trigger 17 by connecting link 56, whereby pivotal movement of the trigger about its axis 18 will cause corresponding reciprocal movement of stem 52 within said air inlet tube. Contraction spring 57 connected at its opposite ends to link 56 and lower body portion 27 of the piston unit, respectively, functions to maintain stem 52 normally seated against seat 44.

As hereinabove mentioned, the blade 14 of the shears is operatively connected to piston unit E. More specifically, blade 14 is provided with an upwardly projecting plate member 61 pivotally secured by pin 62 to a pair of spaced piston rods 63, which, in turn, are rigidly anchored to the lower body portion 27 of the piston unit, such as indicated at 64. As will more fully appear hereinafter, movement of piston unit E under influence of pneumatic pressure within the cylinder will cause blade 14, through connecting elements 61-64, inclusive, to close toward stationary blade 13.

The overall operation of the tool may be described as follows. Assuming the operative elements of the device to be in their normal rest position with the blades 13 and 14 open and with the piston unit fully retracted adjacent the head plate of the cylinder (as shown in Fig. l, for example), the device may be pneumatically actuated so as to forcefully close blades 13 and 14 together through manipulation of trigger 17. More specifically, manual retraction or squeezing of trigger 17 toward handle grip 12 will, through connecting elements 19 and 56, cause valve stem 52 carrying valve head 53 to disengage from seat 49 against the force of spring 57, which normally tends to maintain valve 53 in engagement with said seat 49, as aforesaid. Unseating of valve 53 will thereupon establish communication between the compressory source (not shown) and the head side of cylinder D through aforementioned conduits, connections, chambers, and passages designated at 46, 47, 37, 43, 45, 33, 48, and 49.

Fluid pressure within the cylinder D acting against the piston unit will cause the latter to move within cylinder D in a direction away from head plate 21. Blade 14, in turn, will be caused to move toward its closed position by virtue of its piston rod connection 63 with said piston unit.

It is pointed out that the piston unit will continue to move within the cylinder under influence of air pressure so long as, and only so long as, the operator maintains continuous manual pressure against trigger 17 sufficient to cause and maintain valve stem 52 unseated from seat 49 against the force of spring 57. In this connection, it is recalled that trigger 17 is operatively connected to the piston unit in the sense that the valve stem 52, to which the trigger is connected, is carried by said piston unit. Thus, in order for an operator to maintain the valve stem in unseated position, he must continuously apply a squeezing force against the trigger commensurate with the movement of the piston within its cylinder whereby the trigger at the end of a given cutting stroke is retracted to a position relatively close to handle grip 12. At any time after opening of the air inlet valve and after initiation of movement of the piston unit within the cylinder should an operator release manual squeezing pressure against trigger 17, the force of trigger spring 57 will instantly cause the valve stem to seat.

When the inlet valve 53 is open and the exhaust valve 39 is closed, the force of air pressure acting on the left side of diaphragm31 (tending to open the exhaust valve) is counterbalanced by the combined forces of air pressure acting on the right side of exhaust valve 39 (tending to close said valve) in addition to the resilient diaphragm force and the force of spring 36 acting on said diaphragm also tending to close said valve 39.

Moreover, the resistance of trigger spring 20, acting against said trigger, will function to hold the valve stem 52, inlet tube 37, and valve member 39 relatively stationary with respect to the upper and lower body portions 26 and 27 of the piston unit. These latter elements will, under influence of fluid pressure already contained within the cylinder, continue to move a slight distance farther in the cylinder slidably along said inlet tube so as to cause unseating of exhaust valve 39. More specifically, if at any time during a working stroke an operator releases his grip on the trigger, the air inlet valve will close, and the piston body portion, under influence of air pressure within the cylinder, will continue movement slidably with respect to air inlet tube 37 to a point whereat lower body portion 27 of the piston abuts against annular shoulder 64 provided on said inlet tube, such as shown in Fig. 5 of the drawings. This movement in turn will cause exhaust ports 41 to move away and unseat from valve member 39 (againstthe resilient force of diaphragm 31 and its associated spring 36), thereby establishing exhaust communication from the head side of the cylinder to atmosphere via passages 48 and 49, upper air chamber 32, and exhaust ports 41. Upon exhaust of air from the cylinder, the force of clock spring 16 will return blades 13 and 14 to their normally open position and also cause the entire piston unit to return to its rest position adjacent head plate 21 within said cylinder.

It is to be observed that air pressure within cylinder D does not act upon valve member 39 in such way as to maintain said valve member forcefully seated against exhaust ports ll whereby any considerable force (other than that necessary to overcome the resistance of resilient diaphragm 31 and associated spring 36) is required to open said valve member 39. Stated otherwise, because valve member 39 is carried by resilient diaphragm 31, which in turn is acted upon only by atmospheric pressure in upper chamber 32, the amount of force required to cause opening of the exhaust valve is in no way dependent on the presence or absence of pneumatic pressure within said cylinder.

From the foregoing it is seen that the arrangement of elements comprising the device gives an operator of the tool the ability to maintain control over movement and operation of the working parts at all times during a given working stroke.

Although the present invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be made within the spirit of the invention as limited only by the scope of the claims appended hereto.

I claim:

1. In a pneumatically operated tool of a type having a working part adapted to be moved from a rest position to a working position, the combination comprising: a cylinder having a cylinder head; a piston unit slidably dis posed in said cylinder, said piston unit comprising an upper body portion and a lower body portion secured to and movable with one another in said piston; a central interior cavity formed in said piston unit between said upper and lower body portions; a fluid-tight transverse resilient diaphragm extending across said cavity defining upper and lower chambers, said upper chamber vented to atmosphere, said lower chamber in communication with the head side of said cylinder; a centrally disposed fluid inlet bore formed through the lower body portion of said piston unit for connecting said lower chamber with a compressory source of fluid under pressure located exteriorly of said piston and cylinder; at least one exhaust port formed through said lower body portion connecting said lower chamber with atmosphere; an exhaust valve member mounted on said resilient diaphragm nor mally urged into seated engagement with said exhaust port by said resilient diaphragm for closing communication between said lower chamber and said port, said valve member movable from seated to unseated position with respect to said exhaust port against resistance of said resilient diaphragm, said valve member formed with a central bore having a valve seat in registry with said inlet bore of said lower body portion establishing communication between said inlet port and said lower chamber; an inlet valve stem having a diameter substantially less than the diameter of said inlet bore disposed slidably in said bore defining an open passage between said rod and the interior walls of said bore; a valve head mounted on the inner end of said stem movable reciprocally into and out of seating engagement with said valve seat of said valve member; inlet valve actuating means located ext'eriorly of said cylinder connected to said stem for reciprocating said piston rod and associated valve head out of normal seating engagement with said valve seat of said valve member for establishing fluid communication to the cylinder head side of said cylinder from said compressory source via said air inlet bore, said central bore in said valve member, and said lower chamber; means associated with said inlet valve actuating means for selectively restricting movement of said stem relative to movement of said piston unit within said cylinder under influence of fluid pressure to cause said valve head to engage said valve seat and to cause said valve member to unseat with respect to said exhaust port against the resisting force of said diaphragm to open communication between the head side of said cylinder and said exhaust ports via said lower chamber; and means operatively connecting said piston unit to the working part of said tool.

2. The combination of claim 1 and wherein said last named means comprises a piston rod operatively conmeeting said piston unit with said working part.

3. The combination of claim 1 and wherein said inlet valve actuating means comprises a trigger operable to unseat said valve stem against force of a trigger spring associated with said trigger, and wherein said means associated with said inlet valve actuating means for selectively restricting movement of said stem relative to movement of said piston unit within said cylinder comprises said trigger spring.

4. In a pneumatically operated tool of a type having a working part adapted to be moved from a rest position to a Working position the combination comprising: a cylinder having a cylinder head; a piston unit slidably disposed in said cylinder; an interior hollow cavity formed in said piston unit; an air tight transverse resilient diaphragm extending across said cavity defining upper and lower chambers; said upper chamber vented to atmosphere; said lower chamber in communication with the head side of said cylinder; air inlet means including inlet valve means for supplying air to said lower chamber and to the cylinder head side of said cylinder; air exhaust means including an exhaust valve for exhausting air from said lower chamber and the cylinder head side of said cylinder; said resilient diaphragm connected to said exhaust valve and normally influencing said air exhaust valve to closed position; control means located exteriorly of said cylinder for selectively opening and closing said air inlet valve; and means associated with said air inlet valve for causing opening of said exhaust valve against the influence of said diaphragm upon closing of said air inlet valve.

References Cited in the file of this patent UNITED STATES PATENTS 1,687,047 Trail Oct. 9, 1928 1,831,737 Broussouse Nov. 10, 1931 1,848,923 Almen Mar. 8, 1932 1,872,390 Berry Aug. 16, 1932 1,968,701 Miner July 31, 1934 

